Why support many firings of one Event in a transaction? about sodium HOT 7 CLOSED

You may be right. I think it may be possible to force the person always to deal with simultaneity by making only mergeWith available, not merge. I really haven't thought this through.

P.S. I'm not sure how it works right now, but I'd also define sync such that no changes
caused by the transaction itself are observable within the transaction.

It does work that way.

from sodium.

I strongly recommend reopening this issue. Life is just too complicated with this design where Streams can have multiple firings per transaction:

type S a = [(T, a)]         -- for non-decreasing T values
type C a = (a, [(T, a)])    -- for increasing T values

Why not make them both require increasing T values?

Additionally, at least accum and collectE seem to be broken in the Haskell implementation. They both ignore all but the last firing per transaction.

from sodium.

In reactive-banana, I have also used the "multiple occurrences per Event" model, but I now intend to switch to the proposed "one occurrence per Event" model as well. It forces the programmer to think about simultaneous occurrences explicitly, which I think is a good thing.

from sodium.

All right - I'm persuaded. Let's do it. Now's the time to do it - before I've finished the book. Any counter-arguments?

from sodium.

The only counterargument I can think of is that we lose the completely general instance Monoid (Event a), but I think that's a fair price to pay.

from sodium.

Yeah, already mentioned in my first comment. Fortunately, we can still define

instance Monoid a => Monoid (Event a)

or theoretically even

instance Semigroup a => Monoid (Event a)

from sodium.

94d2653

commit 94d26530c44ef98bce27a78fa1074486a04dcaf1
Author: Stephen Blackheath <[email protected]>
Date:   Fri Jul 24 10:41:10 2015 +1200

    Issue #39: Why support many firings of one Event in a transaction?
    With this change, now we don't in the denotational semantics and in the Java
    version of Sodium. Other versions will follow as they get revamped to be in
    line with the Java version.

from sodium.